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Bottles Vs Cans

The packaging of beer has become a rather controversial subject in recent years. Daniel Cooper looks at the differences between bottles and cans, and whether this makes any difference to the flavour of your beer.

In 2005 a war of words was being waged in the American brewing community. The latest battle had developed over an issue that some might find a little trivial: bottles and cans.

It all started when Jim Koch, president of The Boston Beer Company, released his beer drinkers’ Bill of Rights.

Included in that Bill was the statement that “Beer shall be offered in bottles, not cans, so that no brew is jeopardised with the taste of metal.” This statement was immediately refuted by Dale Katechis, owner of Oskar Blues Brewery based in Colorado, who sent a press release across the country suggesting Koch had been kidnapped by aliens: “Not only is the line about cans tasting like metal damaging to us, but it is also untrue.” And so the argument has continued with no real victor.

The obvious question that springs to mind is does packaging really matter? How many of us really pause for more than a moment’s thought to consider the merits of beer packaged either in a can or bottle? Well it would appear that, much like the brewers, for many beer drinkers the packaging is very important and unsurprisingly the issue boils down to a perception of quality.

So is there really a problem? Does the type of packaging have an impact on the quality of beer and is it possible for beer drinkers to recognise those differences?

The ultimate aim of all beer packaging whether it be bottle, can, keg or cask is to deliver to the consumer beer that is fresh and flavourful. Not all that long ago the majority of beer was served on draught either from the alehouse or brewery but recently a dramatic change in consumption patterns has seen a lot more beer being consumed at home and therefore being packaged in bottle and can.

In terms of preserving the quality of beer, bottles and cans must provide an effective barrier against a number of factors which can lead to a perceivable decline in beer quality. For example the packaging must protect beer against contamination by microbes such as bacteria; it must stop or at least reduce the ingress of oxygen; it must protect the beer from the damaging impact of light and finally the packaging must not contribute any undesirable flavours to the beer.

It is also exceedingly important that the packaging material itself does not have a flavour which can taint the beer. This is the main criticism levelled at beer cans and was the cause of the war of words amongst brewers.

Some drinkers feel that cans impart a metallic flavour to beer. However, to prevent this from occurring all cans used for the packaging of beer are lacquered to provide a barrier between the can and its contents. This means that the chances of a metallic off-flavour in beer imparted from the can are quite low.

Unwanted microbes and the ingress of oxygen can spoil the flavour of beer. With due care and attention the brewer can be confident that the beer going into bottle or can will not spoil due to the presence of either oxygen or microbes. However, once the beer leaves the brewery gates the control that the brewer has over the distribution and selling of their beer is minimal. The packaging must therefore be robust enough to handle any rough treatment that would result in the packaging being compromised allowing oxygen or airborne microbes to get into the beer and spoil it.

The can in this respect perhaps has an advantage over bottles sealed with crown caps. A can that has been damaged sufficiently to compromise the contents is easily recognised and will be removed before being purchased by the consumer. However, with bottles the crown cap can be knocked and loosened sufficiently to allow contamination of the contents with microbes.

Once the microbes have got into the beer through the damaged cap the flavour quality of the beer will deteriorate rapidly. Unfortunately such subtle damage is not easy to spot and may go unnoticed right up to the point of consumption. This inherent weakness of bottle caps also provides a route of entry for oxygen. However, to counteract this problem brewers use oxygen scavenging materials in the plastic liners that help to form an air tight seal between bottle and cap.

Light is one of the biggest causes of perceivable flavour differences between beer that is packaged in bottle compared to beer in cans. The difference in flavour is due to the formation of the compound 3- methylbut-2-ene-1-thiol or MBT. Thankfully brewers prefer a simpler language and so the flavour is more commonly known as light-struck or skunky.

As a quick aside, the light-struck flavour is referred to as skunky because MBT is also found in the obnoxious smelling liquid that skunks spray when they are threatened. Thus if you have ever been unfortunate enough to have been sprayed by an angry skunk you may recognise a similarity between that and the light-struck flavour in beer.

Humans are exceedingly sensitive to MBT with those who are particularly sensitive being able to detect it at levels as low as 0.004 micrograms per litre of beer. To put that into perspective these poor people would be able to detect a hundredth of a gram of MBT dissolved in an Olympic size swimming pool!

MBT forms when Riboflavin, a B-vitamin produced by yeast during fermentation, absorbs light and transfers the energy to the bitter iso-alphaacids, derived from hops. This then causes the release of free radicals, unstable chemical fragments, which react with sulphur containing compounds that naturally occur in beer. The result is the offending MBT.

Interestingly only certain wavelengths of light will trigger this reaction. Brown glass bottles absorb those wavelengths of light thus protecting the beer and cans provide an effective barrier to light. But green and clear glass bottles, that do not absorb the wavelengths of light responsible for MBT formation, will not protect beer.

If you are feeling particularly scientific you can demonstrate this effect at home. The best way of doing this is to find a lager style beer that is packaged in green or clear glass bottles as well as in cans. Expose both the can and bottle of beer to sunlight for a few minutes. Open the bottle, pour the beer into a glass and sniff. Now open the can, pour the beer into another glass and sniff. Any difference in the aroma of the beer will be due to the formation of MBT.

Interestingly although brewers try hard to stop the formation of MBT, studies have shown that for some consumers the aroma of MBT is not an indicator of poor quality beer. This maybe because during a long hot summer many of us will spend many an hour in a pub garden or indulge in alfresco dining where the drink of choice for many is beer.

And with all that sun the beer will develop the MBT flavour and so it becomes a flavour we associate with beer.

And that is, perhaps, the route cause of the problem. What constitutes a bad beer is all down to individual perception and so it is likely that the argument over which is better, beer in can or bottle, will never go away.